Of course he is ready. If he is going immediately after being on the potty, this is a good sign. He understands, and now he just needs the time and practice to get how the muscles work. Just keep at, stay positive, and give him the chance.
2.5 year olds are hard. My son was totally trained at 21 months (including night)...In the last few months (29-31 months), he has started having accidents all the time --his accidents consist of a tablespoon or less of pee in his pants. He is "too busy." I've got him back on track after a rough few months, but the key is to let them do it without nagging too much. Give him the chance to teach himself. So let him wet his pants, gently say "opps, sorry buddy, your pants are wet. Can you take them off and get some new ones?" And just hang in there. He is ashamed. He knows what he is suppose to do but he still needs some time to figure it all out. But I can tell you this, if he is going right after sitting on the potty, he is more than ready, and just needs a little more time. This is a normal stage in potty learning.
Get the book "potty animals" from the library. it's great.
Stay positive, stay calm, and just relax. The more relaxed you can be about it, the easier it will be for him.